Building a raised bed, hugelkultur keyhole garden

I wanted to see what would happen if I combined all of the classic permaculture methods into one beastly raised bed. But I wanted to do it for next to nothing, so I had to scavenge what was available on my property. The only thing I purchased was the netting for the trellis. I combined hugelkultur, sheet mulching, and a keyhole garden into one. Because I used hugelkultur to fill some of the bed, I didn't need to purchase any garden soil to raise it. The keyhole allowed me to access the center while optimizing the total square feet for growing, and because I sunk the keyhole down, I don't have to bend over to reach anything in the bed.

This was the second one I built. The first turned out to be much more of an undertaking than I thought it would. Cutting up all the pieces of wood for the walls and placing them was tedious and time consuming. I promised myself I wouldn't do again, but I had to do another one to complete the symmetry. The first one I didn't sheet mulch or burry the wood as deeply, and the soil turned out too shallow and became weedy. This time I did it right, and had much better success.

I started by outlining a perfect circle 10’ in diameter. It’s easy to do, just pound a stake into the ground, loop a rope around it, make another loop in the rope 5’ out. Then just place a stick through the outside loop and circle around the center stake marking the ground with your stick.

Once I had the circle marked, I dug it out about 1 foot making sure to place all of the topsoil on a tarp for later use. You’ll need at least a 10’ x 10’ tarp.

I found where I wanted the keyhole and dug about another 1-1.5’ deep path to the center, with the eye of the keyhole about 3’ diameter circle. I created a few steps down to the center by digging it 8 inches deeper every foot or so, and placing a piece of wood to retain the soil from the upper step. This is how it looked once the walls were in place.

Cutting and placing the walls of the bed was the most time-consuming part. I had a few areas in my forest that needed some thinning, young pines were crowding some lovely maples. This seemed like a good way to use some of the excess wood that I cleared. I cut about 20 trees, ranging from 3-8” in diameter, into 24-36” pieces and stacked them around the outside of the circle to form the border of the bed. Make sure to cut your pieces for lower keyhole about a foot taller.

For the trellis, I simply cut three 12’ poles from 2-3” diameter maple trees, dug two of them into the ground about 2-3’ deep, and nailed one horizontally onto the tops of the vertical poles.

I filled the bottom with partially rotted wood, and then throw as much vegetable scraps as I had available. I had a garbage bin filled from over the winter. On top of that I threw down leaves and cornstalks from the previous year. Finally, I filled it all back in. I added a sprinkling of wood ash and a bit of pelleted manure I received from a friend and mixed it into the top few inches.

At this point, you have highly disturbed soil that will have tons of weeds ready to germinate. So I placed down a layer of cardboard and mulched with well-rotted pine and oak that had been laying around in my forest decomposing for years.

Finally, I planted the bed! The tomatoes and onions absolutely loved it! The cabbages were demolished by slugs, apparently, the mulch was an attractant for them. I would advise staying away from brassicas the first year or two. Any vegetable that likes woody soils would do great. Tomatoes, peppers, cucumbers, onions, and garlic are what I’ll stick to for now.

The growth was amazing! My tomatoes loved it and grew ridiculously fast. No weeds besides a few grass rhizomes sneaking through here and there. The onions did really well also. It didn’t need much watering with the rotted wood underneath, and mulch up top absorbing and wicking moisture.

the trellis is about 7.5' tall from the bed

With that said, this was a ton of work. Totally not worth it if trying to maximize your efficiency. But it was a fun project and added variety to my growing options. I’m glad I did it, but I won’t be making any more, two is enough.